The present invention is in the field of punching means for providing openings in metal objects and the like and is more particularly directed to a new and unique punch member for use in punching holes in oil and gas well casings for effecting a penetration operation into a surrounding producing geological formation.
Prior U.S. Pat. Nos. 4,640,362 and 4,765,173 to Herman J. Schellstede disclose a punch member 264 having a cylindrical body, and axial bore 353 and channel grooves 354 provided on each side of the punch member. The punch member includes the removable outer tip 264 defined by intersecting planar surfaces 256, 258 to intercept along a line 260. The punch is mounted on element 262 by threaded connection means which can shear in the event of substantial lateral force being applied to the tip member.
While the punch construction of the aforementioned Schellstede patents represented a substantial advance over the art in that it permitted the opening of "doors" on each side of the opening formed in the casing by folding back a portion of the casing in which the opening is provided, such punches do not always provide satisfactory operation. More, specifically the casing would be punched with the "doors" remaining attached to the casing upon completion of the punching operation. However, in some instances the "doors" would not open sufficiently to assure adequate clearance for a high pressure injector lance to move outwardly axially through the axial bore in the punch past the doors into the surrounding formation. The problem of the "doors" not opening adequately was particularly critical when the punching operation was being performed in a casing surrounded by cement. Thus, the problem of always providing a sufficiently wide punch opening for effective deployment of the lance has not been fully solved and the present invention is directed toward the solution of such problem.